The present invention relates to a printer such as a thermal printer, and more particularly to a paper feed mechanism for use therein.
Known paper feed mechanisms for use in printers such as thermal printers typically include a driver angularly movable by a stepping motor, and a rotatable paper feeder such as a paper feed shaft. A ratchet is often disposed between the driver and the rotatable shaft for rotating the shaft in a desired direction only when the driver is angularly moved in one direction for feeding paper.
Although the stepping motor is capable of controlling small incremental motion, the ratchet cannot be angularly moved through a small angle due to the limited pitch of the ratchet teeth of the ratchet. Therefore, the line-to-line interval on the recording paper cannot be varied, or high-resolution graphic patterns cannot be printed. The pitch of the ratchet teeth may be reduced, but only to a limited extent, and a ratchet having the increased number of ratchet teeth required by reducing the pitch would be difficult to form. The printer would also be susceptible to trouble due to wear on the ratchet teeth.